This invention relates in general to inflatable mattresses and cushions and, more particularly, to an improved valve for use with an inflatable mattress or cushion having normally isolated zones to place the normally isolated zones in communication with each other or with the atmosphere in any desired arrangement of communication.
Those individuals who are confined to wheelchairs run the risk of tissue breakdown and the development of pressure sores, which are extremely dangerous and difficult to treat and cure. Typically, much of the individual""s weight concentrates in the region of the ischia, that is, at the bony prominence of the buttocks, and unless frequent movement occurs, the flow of blood to the skin tissue in these regions decreases to the point that the tissue breaks down. Cushions that are especially designed for wheelchairs exist for reducing the concentration of weight in the region of the ischia, and these cushions generally seek to distribute the user""s weight more uniformly over a larger area of the buttocks.
Cellular cushions provide the most uniform distribution of weight and thus provide the greatest protection from the occurrence of pressure sores. These cushions have an array of closely spaced air cells that project upwardly from a common base. Within the base the air cells communicate with each other, and thus, all exist at the same internal pressure. Hence, each air cell exerts essentially the same restoring force against the buttocks, irrespective of the extent to which it is deflected. U.S. Pat. No. 4,541,136 shows a cellular cushion currently manufactured and sold by ROHO, Inc. of Belleville, Ill., for use on wheelchairs.
In a sense the typical cellular cushion provides a highly displaceable surface that tends to float the user. While this reduces the incidence of pressure sores, it detracts from the stability one usually associates with a seating surface. Most of those confined to wheelchairs have little trouble adjusting to the decrease in stability, but for those who have skeletal deformities, particularly in the region of the pelvis and thighs, and for those who lack adequate strength in their muscles, lesser stability can be a source of anxiety. A variation of the ROHO cellular cushion addresses this problem with totally isolated zones and also with cells of varying height. By varying the volume of air between zones, for example, one can accommodate for skeletal deformities while still maintaining satisfactory protection against pressure sores. U.S. Pat. No. 4,698,864 shows zoned cellular cushion with cells of varying height.
Typically, a zoned cellular cushion has a separate filling stem and valve for each of its zones. The user simply opens the valve of each stem and introduces air into the zone for the stem, usually with a hand pump, and then releases the air from the zones until the desired posture is achieved. In a more sophisticated arrangement, a hose kit connects a single pump to a manifold which in turn is connected to the several valves through separate hoses. Those hoses are fitted with separate hose clamps so that the air from the pump may be directed to the cells of the individual zones independently. Likewise, the air can be released from them independently, all by manipulating the clamps.
The hoses of the hose kit lie externally of the cushion and may become entangled in the components of a wheelchair. Furthermore, by reason of their remote locations, the hose clamps are difficult to manipulate. Examples of zoned inflatable cushions that demonstrate significant advantages from zoning are provided in U.S. Pat. No. 5,163,196 and U.S. Pat. No. 5,502,855. The ""196 patent describes a valve for a zoned inflatable cushion such that access to all of the zones is cut off simultaneously because the valve is in a flap which is part of the cushion base and all of the access channels run through the flap. U.S. Pat. No. 5,502,855 utilizes a series of hoses to inflate the cushion and gathers the ends of the hoses in close proximity adjacent one edge of the cushion to prevent tangling. The cushion of the ""855 patent also provides access to the cushion zones from beneath the cushion and provides access to each cell so as to be able to monitor from remote locations.
The present invention is an improvement on valves required by zoned cellular cushions. Heretofore, the zoned cushions employed integral channels which lead from the several zones and which are connected through an integral common manifold and associated valve. The valve generally comprises a flap that is folded over to seal off the ends of the channels or opened to allow communication between the zones through a manifold contained within the flap. Through use it has been determined that these flap-type valves and other prior art zoned cushion valves suffer from some drawbacks. First, in the flap-type valve, the flap has to be manually folded closed and secured with a snap or the like. Often these types of apparatus are difficult for a disabled individual to manipulate. The flap can be awkwardly positioned under the cushion.
A more urgent concern is that the flap valve possibly could leak or fail if the ends of the channels are not appropriately sealed. Continued use and normal wear over time may impair the effectiveness of the flap-type valve. Leaking through the valve could result in unwanted communication between the zones or, in the worst case, could result in loss of air from the cushion and a phenomenon known as xe2x80x9cbottoming outxe2x80x9d where the user""s buttocks come to rest on an uncushioned surface. If the user has no sensation or feeling in the buttocks, for example, the user could xe2x80x9cbottom outxe2x80x9d and not be aware.
The present invention, when employed for example with a zoned cushion having a plurality of inflation zones, provides an easily manipulated valve assembly which can be used to allow fluid communication between two or more zones or can be used to isolate the zones.
In one aspect of the invention, the valve includes a casing having an internal bore and a plurality of openings along the length of the casing which open into the bore. The openings are connected to the individual inflation zones via tubing or the like to place the bore of the casing in communication with the inflation zones. The valve also includes a movable slide seated snugly within the casing bore. The slide has a longitudinal internal bore and a number of openings along its length that communicate with the slide bore. Generally the number of openings in the slide is the same as the number of openings in the valve casing. The slide can be manipulated to align the slide openings with the casing openings to allow the inflation zones to communicate and the air to flow to and from the various inflation zones through the valve slide bore. Correspondingly, the slide can be manipulated to move the slide openings and the casing openings out of alignment, thereby sealing off the inflation zones.
The casing and slide can be cylindrical, ovoid or rectangular in cross section. In one preferred embodiment the slide can be manipulated from side-to-side to move the respective openings into and out of registry. In another exemplary embodiment, the slide is cylindrical in cross section and can be rotated about its longitudinal axis within the casing to move the openings into and out of registry. In another exemplary embodiment, the casing and slide have a circular configuration. In any event, the slide and casing arrangement can include a detent to secure the slide in the desired position. Further, the slide can be color-coded to provide visual indication that the slide is in the desired position.
In another exemplary embodiment, the slide has an air inflation apparatus on one end that can be connected to an air source. Individual zones of the cushion can be inflated simultaneously by introducing air through the valve slide positioned in an open position.
The valve assembly of the present invention can be manufactured apart from the rest of the cushion and appropriately attached to the cushion.